Preparation and application of cobalt-coordinated nitrogen-doped porous carbon-loaded polyacid electrode material
By preparing cobalt-coordinated nitrogen-doped porous carbon-supported polyacid electrode materials, the problems of easy dissolution of polyacid and metal-organic frameworks in solution and low electron transfer rates are solved, and high-efficiency electrocatalytic nitrate reduction and synthesis of ammonia is achieved, improving the activity and stability of the catalyst.
Patent Information
- Application Number
- CN202510723566.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-31
- Publication Date
- 2025-08-29
AI Technical Summary
The polyacid and metal-organic frameworks are easy to dissolve in solution and have low electron transfer rates as electrocatalytic synthesis ammonia electrode materials, which limits the improvement of its electrocatalytic performance.
By preparing cobalt-coordinated nitrogen-doped porous carbon-supported polyacid electrode material, ZnCo-MOF is calcined at high temperature to form Co-CNS, and is compounded with CoMo6 to form CoMo6/Co-CNS composite material. It is prepared by room temperature ultrasonic method to achieve the synergistic effect of polyacid and cobalt particles and improve catalytic performance.
The efficient electrocatalytic nitrate reduction and synthesis of ammonia at room temperature and pressure was achieved, with the Faraday efficiency reaching 90.9% and the ammonia yield reaching 10.27 mg h-1cm-2, significantly improving the activity and stability of the catalyst.
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Figure CN120556079A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electrocatalytic materials, and in particular to the preparation and application of a cobalt-coordinated nitrogen-doped porous carbon-supported polyacid electrode material. Background Art
[0002] Ammonia (NH3) is a globally important chemical, widely used in agriculture (as fertilizer), industry (such as explosives and plastics), and energy storage. Ammonia synthesis primarily relies on the Haber-Bosch process, which requires high temperatures (approximately 400–500°C) and high pressures (150–300 atm), consuming significant amounts of energy and leading to environmental pollution and resource waste. Therefore, the development of green, low-energy alternative technologies for ammonia synthesis has become an urgent need in the field of energy chemistry. Compared with the traditional Haber-Bosch process, electrocatalytic methods can convert renewable energy into ammonia with high energy density and easy storage and transportation. The reaction can be carried out at ambient temperature and pressure, reducing equipment and energy costs, avoiding CO2 emissions, and meeting the requirements of a green, low-carbon economy. Among them, electrocatalytic nitrate-to-ammonia reaction (NO3RR) not only removes the pollutant nitrate from water but also produces high-quality, high-value, zero-carbon, hydrogen-rich fuel ammonia, alleviating environmental pollution while alleviating the energy crisis. The rational design of highly active and selective electrocatalysts is key to achieving efficient NO3RR.
[0003] Metal-organic frameworks (MOFs) are porous materials with high specific surface area, but the poor chemical stability and poor electrical conductivity of most MOFs in water limit their applications. 0 Metal-oxo cluster compounds are formed by the combination of early transition metals and oxygen. Transition metal-substituted polyoxometalates are widely used in electrocatalysis due to their reversible redox activity and electron-rich properties.
[0004] The intrinsic conductivity limitations and insufficient exposure of active sites of MOF-based materials hinder the improvement of electrocatalytic performance. Carbon-based supports (such as nitrogen-doped carbon nanotubes) can accelerate the transfer of electrons on the catalyst surface due to their excellent conductivity, solving the conductivity problem of MOF materials. Through multi-level pore structure and morphology design, cobalt particles loaded with carbon materials can expose more active sites. In addition, the carbon support anchors the cobalt particles, which can inhibit their agglomeration or loss during the reaction and improve the stability of the structure. Cobalt particles and polyacids loaded on carbon materials can improve catalytic performance through a multi-dimensional synergistic mechanism: the carbon support can form a multi-level pore structure under the morphological guidance of the polyacid, increase the exposure of active sites, and promote the mass transfer efficiency of reactants (NO3- / N2); at the same time, the electron-rich characteristics of the polyacid can drive the transfer of electrons from the polyacid to the cobalt particles, accelerate the interfacial charge dynamics process, and help break through the bottleneck of traditional catalytic systems in terms of activity and stability.
[0005] The present invention uses ZnCo-MOF and (NH4)3[CoMo6O 24 H6]·7H2O (abbreviated as CoMo6) as raw material, nitrogen-doped carbon-supported cobalt particle nanomaterials (Co-CNS) were formed by high-temperature calcination of ZnCo-MOF, and then CoMo6 / Co-CNS was prepared by room-temperature ultrasonic method, which showed excellent electrocatalytic performance. Summary of the Invention
[0006] The purpose of the present invention is to solve the problems of easy solubility of polyacids and metal-organic frameworks as electrode materials for electrocatalytic ammonia synthesis in solution and low electron transfer rate. In order to improve the performance of the catalyst in electrocatalytic nitrate reduction to synthesize ammonia, the present invention provides a preparation and application of a cobalt-coordinated nitrogen-doped porous carbon-supported polyacid electrode material.
[0007] To solve the above technical problems, the present invention is achieved through the following technical solutions:
[0008] 1. Preparation of ZnCo-MOF: Dissolve cobalt nitrate and zinc nitrate in distilled water to obtain solution A. Simultaneously, dissolve 2-methylimidazole in distilled water to form solution B. Slowly add solution A to solution B, stir vigorously, wash twice by centrifugation, and finally vacuum dry overnight to obtain ZnCo-MOF.
[0009] 2. Preparation of Co-CNS: ZnCo-MOF was placed in a porcelain boat, then placed in a high-temperature tube furnace, heated to 800°C under an argon atmosphere, and maintained for 3 hours. After cooling, the Co-CNS was taken out.
[0010] Preparation of CoMo6 / Co-CNS Composite Material: Co-CNS was dispersed in distilled water to form a solution. CoMo6 was dissolved in distilled water to form a solution. The two solutions were mixed, ultrasonicated, washed twice by centrifugation, and finally freeze-dried under vacuum to obtain CoMo6 / Co-CNS.
[0011] The mass of the cobalt nitrate described in step 1 is 0.48g to 0.68g, and the mass of the zinc nitrate is 0.48g to 0.68g.
[0012] The mass of the 2-methylimidazole described in step 1 is 2.5-2.6 g.
[0013] The volume of distilled water in step 1 is 50-70 mL.
[0014] The mass of the ZnCo-MOF described in step 2 is 0.15 to 0.25 g.
[0015] The heating in step 2 is carried out under an argon atmosphere, with a heating rate of 1.5 to 2.5° C. / min, a heating temperature of 800° C., and a heating time of 2 to 3 hours.
[0016] The Co-CNS in step 3 is 0.15-0.25 g, and the CoMo6 is 0.15-0.25 g.
[0017] The ultrasonic time in step 3 is 2 to 3 hours, and the centrifugation and washing are 3 to 5 times of washing with distilled water.
[0018] Compared with the prior art, the present invention has the following characteristics:
[0019] The present invention calcined ZnCo-MOF at high temperature to form nitrogen-doped carbon-supported cobalt nanoparticles (Co-CNS), and for the first time prepared a CoMo6 / Co-CNS composite electrode material via a room-temperature ultrasonic method. The synergistic effect between CoMo6 and Co-CNS effectively improved the catalytic performance. This synergistic catalytic effect enabled CoMo6 / Co-CNS to achieve a Faradaic efficiency (FE) of 90.9% and a charge / discharge rate of 10.27 mg h at -0.8 V (vs. RHE). –1 cm –2 ammonia yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 Powder X-ray diffraction (XRD) patterns of Co-CNS and CoMo6 / Co-CNS composites.
[0021] Figure 2 This is a scanning electron microscope (SEM) image of ZnCo-MOF material.
[0022] Figure 3 Scanning electron microscope (SEM) image of Co-CNS material.
[0023] Figure 4 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of CoMo6 / Co-CNS composite materials.
[0024] Figure 5 LSV curves of CoMo6 / Co-CNS composite materials in 0.1M Na2SO4 and 0.1M Na2SO4+0.1MNaNO3 electrolytes.
[0025] Figure 6 Ultraviolet-visible absorption spectra (UV) of CoMo6 / Co-CNS composite materials undergoing ammonia synthesis in 0.1M Na2SO4+0.1M NaNO3 electrolyte at different voltages.
[0026] Figure 7 The ammonia production and Faraday efficiency at different voltages are shown for the ammonia synthesis reaction of CoMo6 / Co-CNS composite material in 0.1M Na2SO4+0.1M NaNO3 electrolyte. DETAILED DESCRIPTION
[0027] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.
[0028] Implementation Case 1
[0029] This example is a preparation case of ZnCo-MOF, which was prepared according to the following method:
[0030] 0.58 g of cobalt nitrate and 0.58 g of zinc nitrate were dissolved in 60 mL of water to obtain solution A. At the same time, 2.624 g of 2-methylimidazole was dissolved in 60 mL of water to form solution B. Solution A was slowly added to solution B, and after vigorous stirring for 3 hours, the solution was washed twice by centrifugation with water and finally dried in vacuum at 60°C overnight to obtain ZnCo-MOF.
[0031] Implementation Case 2
[0032] This embodiment provides a preparation case of an Anderson-type polyacid / Co-CNS composite material, which is prepared according to the following method:
[0033] (1) Preparation of Co-CNS: 0.2 g of ZnCo-MOF was weighed and placed in a porcelain boat. The boat was then placed in a high-temperature tube furnace and heated to 800 °C at a heating rate of 2 °C / min under an argon atmosphere. The mixture was maintained for 3 h and then cooled to remove the Co-CNS.
[0034] (2) Preparation of CoMo6 / Co-CNS composite material: 0.2 g of Co-CNS was weighed and dispersed in 20 mL of aqueous solution to form a solution. The same mass of 0.2 g of CoMo6 was dissolved in 20 mL of water to form a solution. The two solutions were mixed and ultrasonicated for 3 h. The mixture was washed twice by centrifugation with water and finally freeze-dried under vacuum to obtain CoMo6 / Co-CNS.
[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments:
[0036] Figure 1 Shown are powder X-ray diffraction (XRD) patterns of Co-CNS and the CoMo6 / Co-CNS composite. Comparison with data from standard card JCPDS No. 15-0806 demonstrates the successful synthesis of Co-CNS. The diffraction peaks of the CoMo6 / Co-CNS composite at 2θ = 11°, 26°, 29°, and 32° are consistent with those of CoMo6, confirming the successful loading of CoMo6 and demonstrating the synthesis of the CoMo6 / Co-CNS composite.
[0037] Figure 2 Shown is a scanning electron microscope (SEM) image of the ZnCo-MOF material, showing that the ZnCo-MOF material is micron-sized and has a thin willow leaf shape.
[0038] Figure 3 The figure shows a scanning electron microscope (SEM) image of the Co-CNS material. It is observed that the MOF-derived material after high-temperature calcination is still micron-sized, and its morphology maintains a willow-leaf structure without collapse or shrinkage.
[0039] Figure 4 These are scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDS) images of the CoMo6 / Co-CNS composite material. TEM characterization shows that the CoMo6 / Co-CNS composite material presents a three-dimensional nanoflower cluster structure, and the metal cobalt particles uniformly loaded on its surface have a lattice spacing of 0.204 nm (corresponding to the (111) crystal plane of Co). The presence of polyacid particles cannot be identified in the high-resolution image, indicating that their size is too small and there is no agglomeration.
[0040] Figure 5Figure 2 is the LSV curve of CoMo6 / Co-CNS composite material in 0.1M Na2SO4 and 0.1M Na2SO4+0.1MNaNO3 electrolytes. Comparative analysis shows that within the same voltage range, the current density of the nitrate-containing system (0.1M Na2SO4+0.1M NaNO3) is significantly higher than that of the pure sodium sulfate electrolyte, indicating that the CoMo6 / Co-CNS composite material has a certain electrocatalytic nitrate reduction ability.
[0041] Figure 6 The ultraviolet-visible absorption spectra (UV) of the CoMo6 / Co-CNS composite material in the 0.1M Na2SO4+0.1M NaNO3 electrolyte for ammonia synthesis at different voltages are shown in the figure. As shown in the figure, as the voltage increases, the absorbance of the electrolyte that develops color after the catalytic test also gradually increases in the absorbance test.
[0042] Figure 7 The ammonia production and Faradaic efficiency of the CoMo6 / Co-CNS composite material in 0.1M Na2SO4+0.1M NaNO3 electrolyte at different voltages are shown in the figure. As shown in the figure, a Faradaic efficiency (FE) of 90.9% and a yield of 10.27 mg h-1 were achieved at -0.8 V (vs. RHE). –1 cm –2 The ammonia yield is much higher than that of Co-CNS monomer and similar materials. Therefore, the CoMo6 / Co-CNS composite material can be used as a highly efficient electrocatalytic nitrate reduction catalyst for ammonia synthesis.
[0043] In summary: An Anderson-type polyacid / Co-CNS composite material CoMo6 / Co-CNS in Example 2 was successfully prepared by adopting a self-assembly strategy after substrate pre-treatment, and was successfully used in the electrocatalytic nitrate reduction to synthesize ammonia electrode material. The bimetallic MOF material ZnCo-MOF utilizes the low sublimation temperature of Zn, and the Co-CNS produced after calcination not only increases the specific surface area of the material but also increases the conductivity of the substrate material; POM not only acts as a morphology regulator to promote the formation of a flower cluster structure with a high specific surface area of Co-CNS, but also as an electron-rich cluster promotes electron transfer between Co-CNS, thereby achieving the enhancement of the catalytic performance of NO3RR to NH3.
Claims
1. A preparation process of a cobalt-coordinated nitrogen-doped porous carbon-supported polyacid electrode material, characterized by: (1) Preparation of ZnCo-MOF: Dissolve cobalt nitrate and zinc nitrate in distilled water to obtain solution A. Simultaneously, dissolve 2-methylimidazole in distilled water to form solution B. Slowly add solution A to solution B, stir vigorously, wash twice with water by centrifugation, and finally vacuum dry overnight to obtain ZnCo-MOF. (2) Preparation of Co-CNS: ZnCo-MOF was placed in a porcelain boat, which was then placed in a high-temperature tube furnace and heated to 800 °C under an argon atmosphere and maintained for 3 h. The Co-CNS was then taken out after cooling. (3) Preparation of CoMo6 / Co-CNS composite material: Co-CNS was dispersed in distilled water to form a solution. 24 H6]·7H2O (abbreviated as CoMo6) was dissolved in distilled water to form a solution. The two solutions were mixed and then ultrasonically treated. The mixture was washed twice by centrifugation with water and finally freeze-dried in vacuum to obtain CoMo6 / Co-CNS.
2. According to claim 1, the mass of the cobalt nitrate described in step (1) is 0.48g~0.68g, and the mass of zinc nitrate is 0.48g~0.68g.
3. The mass of 2-methylimidazole according to step (1) of claim 1 is 2.5 to 2.6 g.
4. The distilled water volume according to step (1) of claim 1 is 50 to 70 mL.
5. The mass of the Zn / Co-MOF according to step (2) of claim 1 is 0.15 to 0.25 g.
6. According to the heating described in step (2) of claim 1, the heating environment is an argon atmosphere, the heating rate is 1.5-2.5°C / min, the heating temperature is 800°C, and the heating time is 2-3h.
7. The Co-CNS according to step (3) of claim 1 is 0.15-0.25 g and the CoMo6 is 0.15-0.25 g.
8. According to step (3) of claim 1, the ultrasonic time is 2 to 3 hours, and the centrifugation and washing are 3 to 5 times of washing with distilled water.
9. The CoMo6 / Co-CNS prepared by the method for preparing the composite material according to claims 1 to 8 is used for electrocatalytic nitrate reduction to synthesize ammonia.